Abstract: This  paper analyses the policies  of Qing  water  management,official  administration，the technology  of water  projects  and  their effects on  the  Yellow  River  flooding  after it changed  its course  at  Tongwaxiang.In the late Qing Dynasty ,because  grain transportation  by  the Great Canal,which  was  linked with closely  with  the control  of the Yellow River  became less  important ，and also because  of increasing  political  crisis  which threatened  Qing  rule  directly ，the Qing  government took water  management  as a  kind of secondary problem.So  the  funds were greatly reduced and the water conservancy organization  was cut   back.For these reasons,in  addition to  official’s  corruption and the backward  technology。Yellow  River flooding  became  an  “incurable  disease ”.